The possible role of psychosocial factors in the aetiology of insulin dependent (Type 1) diabetes (IDD) will be investigated using the interview technique of Brown and Harris designed to elucidate and quantify the relationship of severe life-events, long-term difficulties and vulnerability factors to chronic diseases. Newly diagnosed insulin dependent diabetics, participating in the Bart's-Windsor Prospective Family Study, will be studied together with a group of sibling controls, with a similar genetic risk of developing diabetes, and an age-and sex-matched group of neighborhood controls. The ratings of stressful life-events and long-term difficulties occurring over the previous 5 years will be compared between the diabetic and control groups. Relationships will be sought between the psychosocial factors and other genetic, immunological and biochemical factors of possible importance in the aetiology of IDD. A development of the same interview technique will be used to investigate the relationship between psychosocial factors, diabetic control, and the prevalence of the large and small vessel disease complications of diabetes in a randomly selected group of adult diabetics, stratified by age, sex, duration and type of diabetes. The prevalence of diabetic complications will be assessed by standardized methods, including the application of the WHO questionnaire for chest pain and intermittant claudication, measurement of arterial blood pressure, a Minnesota-coded ECG, assessment of retinopathy by direct funduscopy and quantification of proteinuria. Diabetic control will be assessed by measurement of urinary and blood glucose and glycosylated haemoglobin. For both studies of disease aetiology and diabetic complications, a long-term follow-up will be initiated to investigate the predictive power of psychosocial factors for future morbidity and mortality in diabetics.